.ajax() : GET, HEAD unable to pass body content.

Even when passing `processData : false` .ajax() uses an regex check to determine whether or not a request is `GET` or `HEAD` which then automatically creates a query string for the request. 

This addresses code first introduced in [this](https://github.com/jquery/jquery/commit/981d1e08eb00f4b5c29ad1f3977a45e30c93ad70#src/ajax.js) commit. Basically what's happening is no matter what, `GET`/`HEAD` data will be forced to a query string, even when implicitly providing `processData : false` in the `settings`.